Wednesday, November 28, 2018

Finally some snow over the Pacific Northwest

There has been a substantial increase in our snowpack during November.  To illustrate, here are the snow depths on November 1 and last night.  Notable increases, particularly over the north Cascades and southern BC..

But even with increases, the snowpack is less than at  the same time last year (see below).

In fact, although there have been considerable increases in higher elevation snowpack the past few weeks, the latest USDA Snotel data shows that the Cascades are still below normal (about 40%), while the northern Sierra Nevada is above normal, as are the western slopes of the Rockies.


The last day has not been kind to our mountain snowpack, with warm, rainy conditions caused by a moderate atmospheric river.  But that is past now and we have been experiencing cooler, unstable conditions, with decent snow showers in the mountains.

The forecast for the next 72 hr  (ending 4 AM Saturday), suggests another half a foot at higher elevations in the  Washington Cascades and huge snow dumps over northern CA and southern Oregon.


Now modern ski areas have considerable capabilities for making snow if the temperatures are cold enough, and there is good news on that front--we are heading into a period of much cooler lower atmosphere temperatures. 

To show this, here are the NOAA/NWS GEFS ensemble air temperature forecasts at the surface for Stampede Pass in the central WA Cascades around 4000 ft  (remember that in an ensemble system we run the forecast model many times to explore uncertainty).  The black line is the average of the forecasts, the ensemble mean, which is usually a very good forecast.  Temperatures really drop the next few days and generally stay below freezing.   Any snow won't be melting and snow making should be fine about 3500 ft.
Crystal Mountain will reopen on Friday, Baker  and Stevens are getting close, and Whistler is open with early season conditions.  Enjoy.

11 comments:

Chris H. said...

I was skiing in the Blue Peak area near Wa pass off the North Cascade Hwy on the 26th. We skied a wind stiffened unconsolidated snowpack until we reached when protected areas in the lower trees.

A quick probe with a ski pole indicated air spaces at the ground snow interface and a snow depth of 38" at 6700'.

At 5500 feet a 2" to 3" melt freeze crust was noted as the base layer with the ground.

More importantly I didn't see any indication of rain crust layers in the snowpack above the base layer crust at 5500'

If the forecast cooler temps and Clear Skies materialize after this weekend, Mountain Travelers will want to take note of surface Frost formation.

This could be a weak layer developing within the snowpack as it gets buried here on the east side north cascades. As always weather depending and spatial variability play a role here.

Also in areas where the snowpack is shallow expect temperature gradients to contribute to the formation of depth hoar.

And most importantly, use your own judgement and Analysis when making decisions involving your personal safety and the safety of members in your group.

Note nwac: please always report accurate information concerning snow instability. Censoring such observational information last year may have been a contributing factor to the first skier avalanche fatality in my area.

I'm not sure that a government administered and funded organization can wipe the public record of such reports.

Nwac also censored a friend of mine reports last year. Apparently nwac doesn't agree with our situational awareness reports when it involves a commercial guide ignoring best safety practice protocols.

Chris H.
Heli-free North Cascades

Aram Attarashany said...

Hello
I like your observations and all, but you NEVER talk about the Blob. You haven’t mentioned any updates on it and I’d love to know if it’s ANY close to being destroyed?

Ellen Baker said...

The skiers and snowboarders are waxing up their gear! We've seen dustings for weeks, but this "incoming" is happy news.

Where it comes to the snow "shortfall," it's not for lack of precipitation. Here in Glacier WA we've already passed the 21" mark for the new rain year (beginning October 1).

I'm not only a weather freak, but I've been a starwatcher/'amateur astronomer' for years and I can't understate how important it is for people closely following climate change to understand celestial mechanics. Here's a link to an extremely informative (strictly instructional, not dogmatic) video about how the Earth and Sun trek through space: https://www.youtube.com/watch?time_continue=1&v=9Ml4_Jv_HkE

Terry McDonald said...

I guess not overly related but can you comment on the blob? It seems to be unscathed and still well established despite observing frequent low pressure systems in the gulf of Alaska throughout Novemeber. This is concerning.

Placeholder said...

@Chris H, your post is full of unexplained jargon, not to mention the undefined "Nwac" which I suppose is an acronym. Were you writing just for yourself, or did you intend to inform any passing non-specialists? If the latter, you need to provide context and definitions.

gnolan said...

Ellen Baker,

Actually lack of rain is a factor in the low snow packs as well as rain melting. If you check the Washington Snotel numbers (generate query from this site:https://wcc.sc.egov.usda.gov/reports/SelectUpdateReport.html) the only basins above normal rainfall are: Lower Snake with an overall basin average of 103% and Central Puget Sound, average 102%. The snow water equivalents are 94% and 40% respectively. The latter number for Central Puget Sound is to my mind at least consistent with Dr. Mass' post regarding the rain melting of snow. The other basins range from 76% to 92% of average rain year totals. All the Puget Sound and the Columbia basin show large differences between snow water amounts and actual precipitation.

The Oregon Snotel report of course shows large deficits in both rainfall and snow water amounts. Interestingly some of the eastern basins are faring better than Cascades. Last few years it has been the other way around. Hood, Sandy, Lower Deschutes (listed together) and Willamette basins are way down. Hood is important for Portland's municipal water supply (which has, incidentally, the lowest dissolved solids for any such water I have analyzed in Oregon).

At any rate this last November storm has brought another half inch this afternoon and its cold enough for us to pick up some accumulation in the Cascades tonight. The rain sounds good.

John Marshall said...

Chris H... thanks for the report on evolving snowpack conditions, and thank you for making it detailed enough to be meaningful to those who understand avalanche mechanisms. Sounds a bit scary if we were to get significant new snow on top of that.

Very nice that some people strap on skis and go measure this stuff.

Chris H. said...

Thank you Placeholder.This is my understanding.


NWAC is the Northwest Avalanche Center, which during late fall through early spring puts out daily regional avalanche forecasts. The forecasters are paid employees of the United States Forest Service.

The u.s. forest service provides funding and administers that branch of nwac.

That government branch of nwac is tangled with a non-profit organization known as "Friends of the Avalanche Center" or whatever they're calling themselves now.

This non profit branch of NWAC solicits membership, accepts donations, sells Safety products to the public and holds public fundraising events. The safety products are lecture series related to snow safety, they pay commercial guides for observational work in the mountains. They also use commercial guides to investigate recreational Avalanche accidents.

NWAC also has control of various weather stations in the mountains which provide telemetry such as temperature snowfall amounts, wind direction and speed on an hourly basis. The forecasters use this information to put out a general forecast for particular region, such as Eastside Stevens Pass to the Canadian border.

So for example in my area there's a station at Washington Pass which reports from two stations one at 5450 feet and one at 6680 feet.

https://www.nwac.us/weatherdata/washingtonpass/now/

Chris H. said...

Local Backcountry skiers have noticed a bias in the reporting from NWAC over recent years. When a near-miss avalanche incident involves a commercial guide or that guide's client, the public reporting becomes inaccurate.

Avalanche information needs to be reported accurately especially as to location.

For example, I believe it was in 2012, we had a particularly persistent weak layer in the our local snowpack that was well documented.

A typical persistent weak layer starts out as surface Frost over an ice crust or maybe a few inches of snow that has been sitting in the cold clear nights. It becomes almost like freeze dried coffee. Very angular faceted grains, grow that don't bond well to the next snow storm. But there are a lot of factors that contribute to that bond strength or not such as temperature during the snow storm.

When that weak layer becomes buried under subsequent snowstorms that favor slab formation, the recipe for slab Avalanche potential is complete. You have a slab over top of a weak layer on top of a sliding surface ie, ice crust.

There are many other permutations of this recipe, such as multiple crusts and faceted snow layers all within one or two inches of the snowpack with a snow slab topper.

Those will form when rain turns to snow then turns to rain then turns to snow.


Chris H. said...

With the recipe is complete, all that is required is a trigger. That can be a skier or snowmobiler or some more snow loading or a dog or energy from a small slide trigger triggering a larger slide. Think Domino's.

So in 2012 I gave a direct warning to two guides concerning a reactive persistent weak layer in a particular area we call the "powder cauche" which is approximately 8 or so miles east of the Washingtonpass crest.

Reactive simply means that snowpack is showing signs of instability (reacting) such as cracking under skier loading or whoomping sounds as the snowpack collapses under a skier. When that happens in Avalanche Terrain, wow scary.

So in 2012, two North Cascade Mountain Guides took a group of three snowboarders out of their FS issued special use permit terrain area and up into the "powder cauche" after recent new snow loading. On the descent, the third snowboarder down boarded over a steep rollover, triggered a 3 foot Crown Avalanche and was buried up to her waist. That Avalanche had the potential to be fatal. I went up 2 Days Later took a look and filed a report on turns all year (now deleted by former site owner Marus)

That Avalanche was reported on the NWAC site as being near Washington Pass and if I remember correctly did not even specify it was a guide related incident.

Chris H. said...

Local skiers were avoiding the snowpack farther East of Washingtonpass in areas such as the "powder cauche" because of the reactive persistence of the weak layer in that zone.

We were instead skiing in the immediate vicinity of Washingtonpass where that weak layer was not reactive, even while skiing on 40 degree coulors.

A commercial guide observed our many local groups from, I assume, the hell bird and publicly shamed us on nwac for skiing steep slopes around the Washingtonpass area, even though those were the dudes having all the problems employing their Avalanche mitigation strategy of "tiptoeing" around the weak layer.

I kid you not, that's the garbage they were spewing.

So here we have the Avalanche Center (nwac) conveying to the public a danger in the Washington Pass area that isn't there at the time.

And not reporting on where the actual location of the reactive persistent weak layer is and being a causal element and a potentially fatal Avalanche.

To my knowledge that Avalanche incident never made it into the NWAC yearly Avalanche summary report.

Note: Areas east of washingtonpass typically receive less snow and a snowpack with less depth is more susceptible to temperature gradients that contribute to the building of grain size in these persistent weak layer faceted snow crystals.(has to do with water vapor transport and reforming from areas of high to low pressure within the snowpack and within the shape of the grains themselves ( someone please check my snow science understanding here as it's been a long time since I studied this stuff).

Flash Forward to last spring where I posted an observation concerning 2 natural release avalanches we had encountered in the "powder cauche" immediately after a new snow loading event. As I said I was frustrated with the inaccurate reporting coming out of nwac. (And there are other examples).

I used the moniker "Vauge observations for money" and reported those Avalanches as being near Washingtonpass, same as nwac does. Nwac deleted that observation from the public page even though they had my email address and phone number and could have asked for clarification.

Two days after that observation was deleted, we had our first skier related Avalanche fatality in our area on the east side of the North Cascades, which happened just a little further east from Washingtonpass. I believe nwac reported the location accurately for that recreational fatality.

So we have a safety organization that puts out inaccurate information concerning safety.

They will also typically hold fundraisers at Alpental and other places where alcohol is served. Imagine a safety organization facilitating the sending out Buzzed and tired skier drivering home on highway 97 at night.

Yes I am critical of this government administered organization.